Spin-labeled heparins as polarizing agents for dynamic nuclear polarization.

A potentially biocompatible class of spin-labeled macromolecules, spin-labeled (SL) heparins, and their use as nuclear magnetic resonance (NMR) signal enhancers are introduced. The signal enhancement is achieved through Overhauser-type dynamic nuclear polarization (DNP). All presented SL-heparins show high (1)H DNP enhancement factors up to E=-110, which validates that effectively more than one hyperfine line can be saturated even for spin-labeled polarizing agents. The parameters for the Overhauser-type DNP are determined and discussed. A striking result is that for spin-labeled heparins, the off-resonant electron paramagnetic resonance (EPR) hyperfine lines contribute a non-negligible part to the total saturation, even in the absence of Heisenberg spin exchange (HSE) and electron spin-nuclear spin relaxation (T(1ne)). As a result, we conclude that one can optimize the use of, for example, biomacromolecules for DNP, for which only small sample amounts are available, by using heterogeneously distributed radicals attached to the molecule.

Thermoresponsive, spin-labeled hydrogels as separable DNP polarizing agents.

In this work, we present thermoresponsive, spin-labeled hydrogels that bear great potential for applications in dynamic nuclear polarization (DNP). In our approach, the water and other polarized molecules are efficiently separated from the radicals needed for DNP by a thermally induced collapse of a polymer network resulting in a prolonged lifetime of the hyperpolarization.

Tunable antibacterial coatings that support mammalian cell growth.

Bacterial infections present an enormous problem causing human suffering and cost burdens to healthcare systems worldwide. Here we present novel tunable antibacterial coatings which completely inhibit bacterial colonization by Staphylococcus epidermidis but allow normal adhesion and spreading of osteoblastic cells. The coatings are based on amine plasma polymer films loaded with silver nanoparticles. The method of preparation allows flexible control over the amount of loaded silver nanoparticles and the rate of release of silver ions.

Surface modification of nanoporous alumina membranes by plasma polymerization.

The deposition of plasma polymer coatings onto porous alumina (PA) membranes was investigated with the aim of adjusting the surface chemistry and the pore size of the membranes. PA membranes from commercial sources with a range of pore diameters (20, 100 and 200 nm) were used and modified by plasma polymerization using n-heptylamine (HA) monomer, which resulted in a chemically reactive polymer surface with amino groups. Heptylamine plasma polymer (HAPP) layers with a thickness less than the pore diameter do not span the pores but reduce their diameter. Accordingly, by adjusting the deposition time and thus the thickness of the plasma polymer coating, it is feasible to produce any desired pore diameter. The structural and chemical properties of modified membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray electron spectroscopy (XPS). The resultant PA membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture, bioreactors, biosensing, drug delivery, and engineering complex composite membranes.